Method and apparatus for dividing thin film device into separate cells

ABSTRACT

A method and apparatus for dividing a thin film device having a first layer which is a lower electrode layer, a second layer which is an active layer and a third layer which is an upper electrode layer, the layers each being continuous over the device, into separate cells which are electrically interconnected in series. The dividing of the cells and the electrical connection between adjacent cells are carried out in a single pass of a process head across the device, the process head performing the following steps in me single pass: a) making a first cut through the first, second and third layers; b) making a second cut through the second and third layers, the second cut being adjacent to the first cut; c) making a third cut through the third layer the third cut being adjacent to the second cut and on the opposite side of the second cut to the first cut; d) using a first ink jet print head to deposit a non-conducting material into the first cut; and e) using a second ink jet print head to apply conducting material to bridge the non-conducting material in the first cut and either fury or partially fill the second cut such to form an electrical connection between the first layer and the third layer, wherein step (a) precedes step (d), step (d) precedes step (e) and step (b) precedes step (e), (otherwise the steps may be earned out in any order in the single pass of the process head across the device). The thin film device may be a solar panel, a lighting panel or a battery

TECHNICAL FIELD

This invention relates to a process of using scribing and ink jetprinting techniques for forming separate electrical cells andinterconnecting them in series to manufacture various thin film devices.In particular, it describes a novel method for forming the cells andseries interconnecting structures in a single step process in solarpanels that have continuous layers of bottom electrode material,semi-conductor material and top electrode material. It is particularlyappropriate for solar panels formed on flexible substrates as the singlestep process eliminates the problems associated with sequential layer tolayer scribe alignment. The method is also appropriate for themanufacture of other thin film devices such as lighting panels andbatteries. The invention also relates to apparatus for carrying out themethod described.

BACKGROUND ART

The usual way to form and interconnect cells in thin film solar panelsinvolves sequential layer coating and laser scribing processes. Tocomplete the structure three separate coating processes and threeseparate laser processes are usually required. It is usual to performthese processes in a six step sequence consisting of a laser stepfollowing each coating step as described below:—

-   -   a) Deposit a thin layer of the lower electrode material over the        whole substrate surface. The substrate is usually glass but can        also be a polymer sheet. This lower layer is often a transparent        conducting oxide such as tin oxide (SnO2), zinc oxide (ZnO) or        indium tin oxide (ITO). Sometimes it is an opaque metal such as        molybdenum (Mo).    -   b) Laser scribe parallel lines across the panel surface at        typically 5-10 mm intervals right through the lower electrode        layer to separate the continuous film into electrically isolated        cell regions.    -   c) Deposit the active electricity generating layer over the        whole substrate area. This layer might consist of a single        amorphous silicon layer or a double layer of amorphous silicon        and micro-crystalline silicon. Layers of other semiconducting        materials such as cadmium telluride and cadmium sulphide        (CdTe/CdS) and copper indium gallium di-selenide (CIGS) are also        used.    -   d) Laser scribe lines through this active layer or layers        parallel to and as close as possible to the initial scribes in        the first electrode layer without damaging the lower electrode        material    -   e) Deposit a third, top electrode layer, often a metal such as        aluminium or a transparent conductor such as ZnO, over the whole        panel area.    -   f) Laser scribe lines in this third layer as close to and        parallel to the other lines to break the electrical continuity        of the top electrode layer.

This procedure of deposition followed by laser isolation breaks up thepanel into a multiplicity of separate long, narrow cells and causes anelectrical series connection to be made between all the cells in thepanel. In this way the voltage generated by the whole panel is given bythe product of the potential formed within each cell and the number ofcells. Panels are divided up into typically 50-100 cells so that overallpanel output voltage is typically in the 50 to 100 Volt range. Each cellis typically 5-15 mm wide and around 1000 mm long. A thoroughdescription of the processes used in this multi-step solar panelmanufacturing method is given in JP10209475.

Schemes have been devised to simplify this multi step process of, makingsolar panels by combining some of the separate layer coating steps. Thisreduces the number of times the substrate has to be moved from a vacuumto an atmospheric environment and hence is likely to lead to improvedlayer quality and increased solar panel efficiency. U.S. Pat. No.6,919,530, U.S. Pat. No. 6,310,281 and US2003/0213974A1 all describemethods for making solar panels where two of the 3 required layers arecoated before laser scribing is performed. The lower electrode layer andthe active layer (or layers) are deposited sequentially and then bothlayers are laser scribed together to form a groove that is then filledwith an insulating material. For U.S. Pat. No. 6,310,281 andUS2003/0213974A1 it is proposed that this groove filling be performed byink jet printing. Following the groove filling, the interconnectionprocedure is as described above with a laser scribe through the activelayer, deposition of the top electrode layer and a final scribe of thetop electrode layer to isolate the cells.

A scheme has also been proposed where all three layers are coated beforeany laser scribing is performed. WO 2007/044555 A2 describes a methodfor making a solar panel where the complete three layer stack is coatedin one process sequence following which laser scribes are made into andthrough the stack. The laser scribe process is complex as it consists ofa single scribe with two different depths. On a first side of the scribethe laser penetrates the complete three layer stack right through to thesubstrate in order to electrically separate the lower electrode layer todefine the cells while on the second side of the scribe the laser onlypenetrates through the top and active layers to leave a region where aledge of lower electrode layer material is exposed. Insulating materialis applied locally to the first side of the scribe that penetrates tothe substrate so that the insulating material covers the edge of thelower electrode layer and the edge of the active layer on the first sideof the scribe. Following this, conducting material is deposited into thescribe so that it bridges the insulating material previously applied andconnects the top electrode layer on the first side to the ledge of lowerelectrode material on the second side.

The process described in WO2007/044555A2 is complex and requires carefulcontrol. Debris generated during the second stage of the dual levellaser scribe process is likely to deposit on the adjacent top surface ofthe ledge of lower electrode material leading to poor electricalconnection. A high level of control is needed to ensure that theinsulating material is placed in exactly the right position on the firstside of the scribe and no material is deposited on top of the ledge oflower electrode material. Extreme accuracy is needed to ensure that theconducting material is placed correctly and does not contact the topelectrode on the second side of the scribe. For all these reasons it isunlikely that cell connections can be made with high reliability by thismethod.

Hence, there remains a requirement for a new cell formation andinterconnection process for solar panels and the like that starts withthe full stack of three layers but proceeds to make the cellinterconnections in a way that is fast, simple and reliable.

Such a process will also be applicable to the formation and seriesinterconnection of cells for the manufacture of other thin film devicessuch as lighting panels or batteries. Like solar panels, such devicesconsist of a lower electrode layer, an active layer and a top electrodelayer all deposited on a rigid or flexible substrate. Operation atvoltages higher than the fundamental single cell voltage can be achievedby dividing the device into multiple cells and connecting the cells inseries. The laser and ink jet cell formation and interconnectionapparatus proposed here is suitable for such an operation.

For lighting panels, the upper and lower electrodes are likely to be ofsimilar materials to those used for solar panels (eg TCOs or metals) butthe active materials are very different. In this case, active layers aremost likely to be organic materials but inorganic materials are alsopossible. Active organic layers are either based on low molecular weightmaterials (so called OLEDs) or high molecular weight polymers (so calledP-OLEDs). Hole and electron transport layers are usually associated withthe active light emitting layers. For these lighting panels, operationis at low voltage and all layers are thin and hence the interconnectionprocess described herein is ideal for dividing the panel into cells andconnecting these in series to allow operation at a substantially highervoltage

For thin film batteries the layers are often more complex. For the caseof a thin film battery based on Lithium ion technology, the lower layerhas two components—a metal layer for current collection and a LithiumCobalt Oxide (LiCoO3) layer that functions as a cathode. The upper layeralso has two components—a metal layer for current collection and a TinNitride (Sn3N4) layer that functions as an anode. In between these twolayers is the active layer—a Lithium Phosphorous OxyNitride (LiPON)electrolyte. For such batteries, operation is at low voltage and alllayers are thin and hence the interconnection process described hereinis ideal for dividing the battery into cells and connecting these inseries to allow operation at a substantially higher voltage

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a methodfor dividing a thin film device having a first layer which is a lowerelectrode layer, a second layer which is an active layer and a thirdlayer which is an upper electrode layer, all the layers being continuousover the device, into separate cells which are electricallyinterconnected in series, the dividing of the cells and the electricalconnection between adjacent cells all being carried out in a single passof a process head across the device, the process head performing thefollowing steps in the single pass:

-   -   a. making a first cut though the first, second and third layers;    -   b. making a second cut though the second and third layers, the        second cut being adjacent to the first cut;    -   c. making a third cut through the third layer, the third cut        being adjacent to the second cut and on the opposite side of the        second cut to the first cut;    -   d. using a first ink jet print head to deposit a non-conducting        material into the first cut; and    -   e. using a second ink jet print head to apply conducting        material to bridge the non-conducting material in the first cut        and either fully or partially fill the second cut such that an        electrical connection is made between the first layer and the        third layer,    -   wherein step (a) precedes step (d), step (d) precedes step (e)        and step (b) precedes step (e), otherwise the steps may be        carried out in any order in the single pass of the process head        across the device.

According to a second aspect of the invention, there is providedapparatus for dividing a thin film device having a first layer which isa lower electrode layer, a second layer which is an active layer and athird layer which is an upper electrode layer, all the layers beingcontinuous over the device, into separate cells which are electricallyinterconnected in series, the apparatus comprising a process head onwhich are provided:

-   -   a. one or more cutter units for making a first cut though the        first, second and third layers and a second cut though the        second and third layers' adjacent to the first cut and a third        cut through the third layer adjacent to the second cut;    -   b. a first ink jet print head for depositing a non-conducting        material into the first cut; and    -   c. a second ink jet print head for applying conducting material        to bridge the non-conducting material in the first cut and        either fully or partially fill the second cut so that an        electrical connection is made between the first layer and the        third layer, the apparatus also comprising:    -   d. drive means for moving the process head relative to the        panel; and    -   e. control means for controlling movement of the process head        relative to the device and actuating said one or more cutter        units and said first and second ink jet print heads so that        division of the panel into separate cells and the formation of        an electrical connection between adjacent cells can all be        carried out in a single pass of the process head across the        device.

In the detailed description of the invention that follows the cutterunits that are used to form the cuts through the various layers are allbased on lasers, the beams from which are focussed to ablate and removematerial to form the isolating cuts. This is the preferred method forforming the cuts but other methods of cutting may also be used. Onealternative method for forming cuts is mechanical scribing with finewires or styli. Such mechanical scribing can be used instead of lasercutting for forming all or some of the first, second or third cuts.

Like the invention described in WO 2007/044555 A2, this inventioninvolves the processing of a thin film device having a complete stack ofthree layers but subsequent layer cutting and ink jet processing is lesscomplex and much more robust compared to that described in WO2007/044555 A2. As in WO2007/044555 A2, all three coatings are appliedsequentially before any layer cutting or material deposition by inkjetting. Ideally, these coatings might be applied in a single vacuumprocess but this is not essential. The key point of our invention isthat following the deposition of the coatings a single combined layercutting and ink jet process is used to make the cell inter-connections.A “single combined process” should be understood to mean that all thecutting processes and all the associated ink jet based materialdeposition processes are performed by means of the movement of a processhead in a single pass across all or part of the solar panel in a planeparallel to the substrate surface and in a direction parallel to theboundary between the cells. All cutter units and all ink jet print headsrequired to make one or more cell interconnections are attached to asingle process head and hence all items move together at the same speedacross the panel.

The sequence in which the various layer cutting processes and thevarious ink jet deposition processes are applied to the substrate canvary depending on the materials used. The various layer cutter units andink jet print heads are attached to the process head in such positionsthat the correct sequence is achieved as the process head moves withrespect to the substrate.

For simplicity of illustration, the layer cutting processes willhenceforth be described with reference to laser ablation. It should benoted, however, that all or some of these laser cutting processes may bereplaced by a mechanical scribing process (or other cutting process).

To form a single cell interconnection structure between adjacent firstand second cells, three adjacent laser beams, delivered by threeadjacent beam delivery units attached to the process head move togetherwith respect to the substrate in the direction parallel to the boundarybetween the cells to make three parallel adjacent scribes to differentdepths in the various layers. A first laser beam makes a first scribeline that defines the edge of the first cell. This first scribepenetrates all layers down to the substrate. A second laser beam locatedon the second cell side of the first scribe makes a second scribe linethat penetrates through all layers except the lower electrode layer. Athird laser beam situated on the second cell side of the second scribemakes a third scribe that penetrates the upper electrode layer. Thisthird scribe defines the extent of the second cell. The precise order inwhich these three laser processes is performed is not critical butpreferred orders are discussed below.

A first ink jet printing process follows some or all of the laserprocesses. For this first printing process a first ink jet head movesacross the substrate surface with at least one nozzle arranged to printa fine line of insulating ink that fills the first laser scribe. Thisink can be of the thermally curing type in which case heat is appliedlocally to the deposited liquid immediately after deposition to cure theinsulating ink to make an insulating solid line of material that fillsthe first scribe. Alternatively following all laser and ink jetprocesses heat is applied to the whole of the substrate to cure thelines of insulating ink to make insulating solid lines of material thatfill all the first scribes on the substrate. This whole substrate curingprocess can take place on the same apparatus that performs the laserscribing and ink deposition processes but in practice it is more likelythat this curing is performed on separate apparatus.

The insulating ink can also be of the UV curing type. In this casecuring is performed by means of a UV lamp or other appropriate UV lightsource in which case UV radiation is applied locally to the depositedliquid immediately after deposition to cure the insulating ink to makean insulating solid line of material that fills the first scribe. Thedepth of the insulating layer in the scribe is a small as possibleconsistent with being continuous and having no pinholes. The width ofthe line of insulating material is such that it fully contacts the lowertwo exposed layers on the first cell side of the first scribe so thatthese layers are protected from material subsequently applied in asecond ink jet printing process. Some degree of insulating inkoverfilling on both sides of the first scribe is allowed and may even bedesirable but ideally the lateral extent of the over filling should bekept to a value that is less than the width of the first scribe.

The second ink jet printing process takes place following some or all ofthe laser processes and following the first ink jet printing process.For this second ink jet printing process a second ink jet head is movedover the substrate surface with at least one nozzle arranged to print aband of conducting ink that is wide enough to make electrical contactwith the top electrode material on the first cell side of the firstlaser scribe, to straddle the insulating ink material in the firstscribe and enter the second scribe to make electrical contact the lowerelectrode layer material of the second cell. The insulating ink in thefirst scribe may be either cured or uncured at the time of applicationof the conducting ink. If the insulating ink is uncured then thecomposition of the conducting ink is such that the solvent does notsignificantly perturb or dissolve the uncured insulating ink material.The conducting ink is likely to be of the thermally curing type, inwhich case, following all laser and ink jet processes, heat is appliedto the whole substrate to cure the bands of conducting ink to form solidconducting bands of material. In this way electrically conductingbridges are formed that connect the top electrode in one cell to thelower electrode layer in the next cell. The depth of the conductinglayer is a small as possible consistent with being robust and havingadequately low electrical resistance. The width of the line ofconducting material is such that it fully contacts a region of the firstcell top electrode material on the first cell side of the first scribeand fully fills the second scribe. Some degree of conducting inkoverfilling on the first cell side of the first scribe and the secondcell side of the second scribe is allowed and may even be desirable butideally the lateral extent of the over filling should be kept to a valueless than the scribe width.

Because three separated laser scribes are used it is possible toindividually optimize the laser process parameters for each scribe toeliminate the possibility of substrate or lower layer damage, reducerisk of forming electrical shorts between layers and minimize debrisdeposition.

It is also possible to attach the individual beam delivery heads to theprocess head in positions spaced along the direction of movement of thehead with respect to each other so the positions of the ink jet headsdefines the sequence in which processes are applied to the substrate. Apreferred sequence for the 5 processes is:—

-   -   a. First laser scribe through all layers down to the substrate        surface to define the extent of the first cell    -   b. First ink jet process to deposit insulating ink in the first        laser scribe    -   c. Second laser scribe process through the top two layers down        to the lower electrode layer    -   d. Second ink jet process to apply a band of conducting ink over        the insulating ink to form a conducting bridge from the top        electrode on the first cell side to the lower electrode on the        second cell side    -   e. Third laser scribe process through the top electrode layer to        isolate the first and second cells and define the extent of the        second cell

With this sequence of laser and ink jet processes, lower layers in thestack remain protected from laser ablation debris and stray inkmaterials arising from earlier processes until just before exposure andthe total cell interconnection process becomes very robust.

For example, some debris generated by the first laser process and someinsulating ink deposited by the first printing process may form on thesubstrate surface in the region where the second laser process scribesthrough to expose the lower electrode. If the second laser processprecedes the first ink jet printing process, or the first laser process,then any stray debris or insulating ink may enter the second laserscribe region and contaminate the exposed lower electrode layer. Leavingthe second laser process until after both the first laser and first inkjet printing processes means that the lower electrode layer in the areaof the second laser scribe remains protected and during the second laserprocess any re-deposited debris and any insulating ink in that area isremoved as the laser ablates the top two layers.

As another example, debris generated by the second laser process andsome conducting ink deposited by the second printing process may form onthe substrate surface in the region where the third laser processscribes through to separate the top electrode layer. If the third laserprocess precedes the second printing or the second or even first laserprocesses then any stray debris or ink may deposit on the top surface ofthe second cell in the third laser scribe region and may cause anelectrical connection across the scribe region. Leaving the third laserscribe process until after both the first and second laser processes andafter both the first and second printing processes means that thissource of interconnect failure is eliminated.

The preferred process sequence given above is appropriate if thecomponents of the process head are to be operated as the head moves inonly one direction across the panel (the components being inoperative asthe head returns to its initial position). If, however, the componentsof the head are to be operative as the process head is moved in either(or both) directions over the panel, then an alternative sequence ispreferred. This sequence for the 5 processes is:—

-   -   a. First laser scribe through all layers down to the substrate        surface to define the extent of the first cell    -   b. Second laser scribe process through the top two layers down        to the lower electrode layer    -   c. Third laser scribe process through the top electrode layer to        isolate the first and second cells and define the extent of the        second cell    -   d. First ink jet process to deposit insulating ink in the first        laser scribe    -   e. Second ink jet process to apply a band of conducting ink over        the insulating ink to form a conducting bridge from the top        electrode on the first cell side to the lower electrode on the        second cell side

With this sequence, by mounting two ink jet heads for delivery ofinsulating ink and two ink jet heads for delivery of conducting ink on asingle process head, the head can be operated in either direction oftravel. In this case, the order in which the separate laser and ink jetheads are mounted on the head is as follows:—

-   -   a. first conducting ink jet head    -   b. first insulating ink jet head    -   c. first, second and third laser beams    -   d. second insulating ink jet head    -   e. second conducting ink jet head.

When the process head moves in one direction all three laser beams areoperated but only the first insulating and first conducting ink jetheads are operated so that the process sequence is c, b and a. When theprocess head moves in the opposite direction all three laser beams areoperated but in this case the first ink jet heads are inactive and thesecond ink jet heads are activated so that the process sequence is c, dand e.

Some processes have to precede others:—

-   -   1) The first laser scribe process must always precede the first        printing process    -   2) The first printing process must always precede the second        printing process    -   3) The second laser scribe process must always precede the        second printing process.

Within these rules several different process sequences are possible butthe one given above is preferred. It is also preferred that curing oflines of both insulating and conducting inks is performed thermally andthat this thermal curing process is carried out simultaneously to allthe lines of insulating ink and conducting ink on the substrate usingseparate apparatus to that used to carry out the laser and ink jetdeposition processes.

The lasers used to create the first, second and third cuts are generallyof the pulsed Q-switched type operating in the IR to UV range (ie withwavelengths from 1080 nm down to 340 nm). In the simplest case, a singlelaser is used with a single focussing lens to create all three cutsassociated with a single interconnect structure. Hence, in this case, itis necessary to divide the single beam into three components to formthree focal spots on the substrate surface. Cut separation in aninterconnect is generally small (in the 0.1 to 0.2 mm range) so apreferred way to make the three-way beam division is to use adiffractive optical element (DOE) or special multi-facetted prismaticelement positioned before a single focussing lens. Such devicesintroduce small angular deviations to parts of the laser beam which giverise to focal spot separations of the required value at the focus of thelens. Such devices also allow the relative power in individual beams tobe set by suitable device design.

Another preferred method to create the first, second and third beamsassociated with a single interconnect structure involves the use of twodifferent pulsed lasers and a single focussing lens. In this case, thelasers can have different wavelengths which is often advantageous interms of optimised removal of upper layers without damaging lower layersof material. When two lasers are used to form the three beams requiredfor a single interconnect structure, a first laser is used to form twoof the beams and the second laser the third beam. A DOE or simplebiprism is used to divide the first beam into two components in the sameway as discussed above for the case where only a single laser is usedand the beam is divided into three components. The beam from the secondlaser is combined with the beams created from the first laser and allbeams are passed through a single focussing lens to create three spotswith the required separation on the substrate surface. Beam combiningwith a special mirror that transmits one beam and reflects another usingpolarisation or wavelength differences between first and second lasersis commonly used.

Servo motor driven stages are used to move the substrate with respect tothe process head. In operation, the process head can be stationary withthe panel moving in two axes in a series of linear moves in thedirection parallel to the cell directions each pass across the substratebeing followed by a step in the orthogonal direction. The process headmay process a single cell interconnect on each pass or in a preferredsituation may process multiple interconnects on each pass. Other stagearrangements are possible. A preferred arrangement has the substratemoving in one axis and the process head moving in the other. Anarrangement where the process head moves in two orthogonal axes over astationary substrate is also possible.

Other preferred and optional features of the invention will be apparentfrom the subsidiary claims of the specification.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described, merely by way of example, withreference to the accompanying drawings, in which:

FIG. 1 shows a standard method for electrically interconnecting cells ina thin film solar panel;

FIGS. 2A to 2F illustrate a standard method using separate laserscribing and material deposition steps to form and interconnect cells inthe case where only the lower electrode layer has been applied beforelaser scribing commences. This sequence of processes is a standard,known solar panel production method;

FIGS. 3A to 3F illustrate a standard method using separate laserscribing and material deposition steps to form and interconnect cells inthe case where the lower electrode layer and the active layer have bothbeen applied before laser scribing commences. This sequence of processesis also known;

FIGS. 4A to 4E illustrate a standard method using separate laserscribing and material deposition steps to interconnect cells in the casewhere the lower electrode layer, the active layer and the upperelectrode layer have all been applied before laser scribing commences;This sequence of processes is also known;

FIG. 5 shows an enlarged, schematic, plan view of part of apparatusaccording to a first embodiment of the invention. It shows anarrangement of the three laser beams and two ink jet nozzles that areattached to a process head in order to make a single cell interconnectstructure;

FIGS. 6A to 6F show a preferred sequence of laser and ink jet processesdelivered to a substrate surface by the apparatus shown in FIG. 5;

FIG. 7 shows an enlarged, schematic, plan view of part of apparatusaccording to a second embodiment of the invention;

FIGS. 8A to 8D show a preferred sequence of laser and ink jet processesdelivered to a substrate surface by the apparatus shown in FIG. 7;

FIG. 9 shows an enlarged, schematic, plan view of apparatus according toa third embodiment of the invention;

FIGS. 10A to 10E show a sequence of laser and ink jet processesdelivered to a substrate surface by the apparatus shown in FIG. 9;

FIG. 11 shows an enlarged, schematic, plan view of apparatus accordingto a fourth embodiment of the invention;

FIGS. 12A to 12E show a time sequence of laser and ink jet processesdelivered to a substrate surface by the apparatus shown in FIG. 11;

FIG. 13 shows an enlarged, schematic, plan view of part of a processhead used in a preferred embodiment of the invention. It shows howarrays of laser beams and arrays of ink jet nozzles can be mounted onthe process head and used to form multiple adjacent cell interconnectingstructures in a single pass over the panel as illustrated in FIGS. 5 and6;

FIG. 14 shows an enlarged, schematic, plan view of part of a processhead used in a further embodiment of the invention. It demonstrates howarrays of laser beams and arrays of ink jet nozzles can be mounted onthe process head and used to form multiple adjacent cell interconnectingstructures in a single pass over the panel as illustrated in FIGS. 7 and8;

FIG. 15 shows an enlarged, schematic, plan view of apparatus accordingto a fifth embodiment of the invention; it shows an arrangement of thethree laser beams and two sets of associated ink jet nozzles that areattached to a process head in order to make single cell interconnectstructures by moving the process head in either direction;

FIG. 16 shows an enlarged, schematic, plan view of part of a processhead used in the fifth embodiment of the invention. It demonstrates howan array of laser beams and, two arrays of ink jet nozzles can bemounted on the process head and used to form multiple adjacent cellinterconnecting structures in a single pass in either direction over thepanel as illustrated in FIGS. 7 and 15;

FIG. 17 shows apparatus that uses a diffractive optical element to splita beam from a single laser to form first, second and third laser beams;

FIGS. 18A and 18B show how a prismatic type optical component is used tosplit abeam from a laser into three angularly separated beams;

FIG. 19 shows apparatus that uses a prismatic type optical component tosplit a beam from a single laser to form first, second and third laserbeams;

FIG. 20 shows apparatus that uses a bi-prism or diffractive opticalelement to split a beam from a single laser to form two laser beamswhich are then combined with a third beam;

FIG. 21 shows apparatus for moving a substrate in two directions withrespect to the process head; and

FIG. 22 shows apparatus for controlling the operation of the laser orlasers, the ink jet heads and the motion systems.

For simplicity, the figures illustrate layer cutting processes as beingof the laser ablation type. It should be noted, however, that all orsome of these laser cutting processes may be readily replaced by amechanical scribing process or other cutting process.

DETAILED DESCRIPTION OF DRAWINGS

FIG. 1 is prior art and shows a section of a solar panel that has beensubdivided into separate cells which have been electrically connected inseries by means of the three layer coating and three laser scribingprocesses. The substrate 11 has three layers: a lower electrode layer12, an active layer 13 and a top electrode layer 14. Laser scribes 15,16 and 17 permit electrical connections and isolations between adjacentcells to be formed.

FIG. 2 is prior art and shows a region of a solar panel in theneighbourhood of the boundary between two adjacent cells. FIGS. 2A to 2Fshow the various coating ° and laser scribing stages that are used toform and connect the cells. The substrate 21 is generally glass orplastic but can also be made of another insulating material. It can alsobe metal or a metal with an insulating coating. In FIG. 2A the lowerelectrode layer 22 has been applied to the substrate 21. FIG. 2B showshow a first laser scribe line 23 through the lower electrode layer 22 tothe substrate 21 defines the cell boundary. In FIG. 2C an active layer24 is applied to the substrate filling the first laser scribe line. FIG.2D shows how a second laser scribe line 25 parallel to the first line 23separates the active layer 24. In FIG. 2E a top electrode layer 26 isapplied to the substrate filling the second laser scribe line 25. FIG.2F shows the final stage where a third laser scribe line 27 parallel tothe second line 25 completely penetrates the top electrode layer 26 andpartially or fully penetrates the active layer 24.

FIG. 3 is prior art showing an example of a case where both the lowerelectrode layer and the active layer are applied before cellinterconnection proceeds. FIG. 3A shows the substrate 31 with twocoating layers 32 and 32′ applied. FIG. 3B shows a first laser scribeline 33 penetrating the two layers 32, 32′ as far as the substrate. FIG.3C shows how an insulating fluid 34 is applied into the first laser cut33. One method for doing this is to use an ink jet nozzle. The fluid 34is subsequently cured to form a solid. FIG. 3D shows how a second laserscribe line 35 penetrates the upper 32′ of the two layers only. FIG. 3Eshows how a top electrode layer 36 is applied so filling the secondlaser scribe line 35. FIG. 3F shows the final stage where a third laserscribe line 37 completely penetrates the top electrode layer 36 andpartially or fully, penetrates the active layer 32′.

FIG. 4 is prior art showing an example of a case where all three layers;the lower electrode layer, the active layer and the top electrode layerare applied before cell interconnection proceeds. FIG. 4A shows thesubstrate 41 with a stack of layers consisting of a lower electrodelayer 42, an active layer 42′ and an upper electrode layer 42″. Theselayers are applied sequentially without any intermediate laserprocesses. FIG. 4B shows a first wide laser scribe line 43. This scribeline 43 penetrates only the top two layers 42′, 42″ of the layer stackand leaves the lower electrode layer 42 intact. FIG. 4C shows how asecond narrower laser scribe line 44 is made inside and to one side ofthe first scribe line 43. This second scribe line 44 penetrates thelower electrode layer 42 and leaves a ledge 45 of lower electrodematerial 42 remaining. FIG. 4D indicates how an insulating fluid 46 isapplied into the first laser scribe 43 by means of an ink jet nozzle.The fluid 46 is subsequently cured to form a solid. The application ofthe fluid into the scribe 43 is carefully controlled so that it isapplied only to a first side of the scribe line 43 that side being theside that penetrates to the substrate and is opposite to the side wherethe ledge 45 of lower electrode material 42 exists. FIG. 4E shows thefinal stage where conducting fluid 47 is deposited into the scribe lineso that it bridges the insulating material 46 and makes an electricalconnection between the top electrode layer 42″ on the first side of thescribe 43 to the ledge 45 of lower electrode material on the second sideof the scribe 43. Care has to be taken to ensure that the conductingmaterial 47 does not contact the top electrode 42″ on the second side ofthe scribe 43.

FIG. 5 shows a first, preferred, version of part of the apparatusaccording to the invention. It shows a first arrangement of the threelaser beams and two ink jet nozzles that are attached to a process headin order to make a single cell interconnect structure. A solar panel 51has multiple cells along its length in the direction Y. This means thatinterconnections are made by relative motion of the process head withrespect to the panel in the direction X. An area of the panel 52 thatincludes a region where adjacent cells are connected is shown enlargedon the right side of the figure and shows part of the moving processhead with its associated laser beams and ink jet nozzles that correspondto a single cell interconnect structure. First, second and third laserbeams 53, 53′ and 53″ make a first scribe 54 through all three layers, asecond scribe 54′ through the top two layers and a third scribe 54″through the top layer, respectively. The figure indicates the processhead and attached laser beams moving in the X direction with respect tothe substrate such that, on the substrate surface, the first laser beam53 is in advance of the second laser beam 53′ which is likewise inadvance of the third laser beam 53″. An ink jet nozzle 55 is attached tothe process head and is situated on a line that is parallel to the Xdirection and passes through the position of the first laser beam 53.This nozzle 55 injects a stream of insulating fluid 56 to fill the firstlaser scribe line 54. A second, larger ink jet nozzle 57, or multiplesmaller nozzles, is also attached to the process head and is situated inthe X direction such that when the process head is moving over thesubstrate, the second ink jet nozzle 57 follows the first ink jet head55 and the second laser beam 53′. This second ink jet nozzle 57 injectsa stream of conducting fluid 58. The nozzle is situated in the Ydirection such that the fluid 58 is deposited on the substrate surfaceand forms an electrically conducting bridge over the previously appliedinsulating fluid 56, the bridge extending from the upper electrodesurface on the left side of the first scribe 54 to the lower electrodesurface at the base of the second scribe 54′. As the process head movesacross the substrate in the X direction, the order of the five processescarried out to form and complete the interconnect structure is asfollows:—

-   -   1) Laser scribe line 54 through all 3 layers by first laser beam        53    -   2) Fill first laser scribe line 54 with insulating ink 56        delivered by first ink jet nozzle 55    -   3) Laser scribe line 54′ through top 2 layers by second laser        beam 53′    -   4) Form conducting bridge across first laser scribe line 54 to        second laser scribe line 54′ with conducting ink 58 delivered by        second ink jet nozzle 57    -   5) Laser scribe line 54″ through top layer by third laser beam        53″

Instead of moving the process head over a stationary substrate surfacein the direction X (as shown), the same sequence of laser and ink jetprocesses can be achieved by holding the process head stationary andmoving the panel in the opposite X direction.

FIG. 6 shows the sequence of the laser and ink jet processes deliveredto the substrate surface by the apparatus shown in FIG. 5. FIG. 6A showsa substrate 61 on which a stack of layers 62 consisting of a lowerelectrode layer, an active layer and an upper electrode layer has beendeposited. These layers are applied sequentially without anyintermediate laser processes. FIG. 6B shows the first of the three laserprocesses that are then carried out. A first laser scribe line 63 ismade that penetrates all 3 layers 62 as far as the substrate 61. Afterthe first laser process has been completed, insulating material isimmediately applied by ink jet printing into the first laser scribe line63. FIG. 6C shows how an insulating fluid 64 is applied into the firstlaser scribe line 63 by means of a first ink jet nozzle (not shown). Thefluid 64 is immediately UV cured or later thermally cured to form asolid FIG. 6D shows the next step where a second laser scribe line 65 ismade parallel to the first scribe line 63 through the top two layers asfar as the lower electrode layer. FIG. 6E shows the next step wherefluid 66 that is conducting or contains conducting particles is appliedby means of a second ink jet nozzle (not shown) over the insulatingmaterial 64 in the first scribe line 63 and also into the second laserscribe line 65. The fluid 66 is subsequently thermally cured to form asolid. The conducting material 66 forms a bridge over the insulatingmaterial 64 to electrically connect the top electrode layer on the leftside to the bottom electrode layer on the right side to connect adjacentcells in series. FIG. 6F shows the last step in the interconnectionprocess where a third laser scribe line 67 that penetrates the upperlayer is made parallel to and beside the second scribe line 65 on theside away from the first scribe line 63. This scribe can also penetratepartially or fully into the active layer but must not damage the lowerelectrode layer. The advantages of the preferred sequence of processesshown in FIGS. 5 and 6 are:—

-   -   1) the second laser scribe process can be used to remove any        debris generated by the first laser scribe process that deposits        in the region of the second scribe line as well as deposited        insulating ink that may have spread across the surface of the        upper electrode into the region of the second scribe line, and    -   2) the third laser scribe process can be used to remove any        debris generated by the second laser scribe process that        deposits in the region of the third scribe line as well as        deposited conducting ink that may have spread across the surface        of the upper electrode into the region of the third scribe line

FIG. 7 shows a second version of part of apparatus according to a secondembodiment of the invention. It shows a second arrangement of the threelaser beams and two ink jet nozzles that are attached to the processhead in order to make a single cell interconnect structure. A solarpanel 71 has multiple cells along its length in direction Y. This meansthat interconnections are made by moving the process head with respectto the panel in the X direction. An area 72 of the panel that includes aregion where adjacent cells are connected is shown enlarged on the rightside of the figure and shows part of the moving process head with itsassociated laser beams and ink jet nozzles that correspond to a singlecell interconnect structure. First, second and third laser beams 73, 73′and 73″ make a first scribe 74 through all three layers, a second scribe74′ through the top two layers and a third scribe 74″ through the toplayer, respectively. The figure shows the process head and attachedlaser beams moving in the X direction such that on the substrate surfacethe first laser beam 73 is in advance of the second 73′ which islikewise in advance of the third 73″. Other ordering of these threebeams is possible or all three can be in a line moving across thesubstrate surface. An ink jet nozzle 75 is attached to the process headand is situated on a line that is parallel to the X direction and passesthrough the position of the first laser beam 73. This nozzle 75 injectsa stream of insulating fluid 76 to fill the first laser scribe 74. Asecond larger ink jet nozzle 77, or multiple smaller nozzles, is alsoattached to the process head and is situated in the X direction suchthat when the process head is moving over the substrate the second inkjet head 77 follows the first ink jet head 75. This second ink jetnozzle 77 injects a stream of conducting fluid 78. The nozzle 77 issituated in the Y direction such that the fluid 78 is deposited on thesubstrate surface and forms an electrically conducting bridge over thepreviously applied insulating fluid 76, the bridge extending from theupper electrode surface on the left side of the first scribe 74 to thelower electrode surface at the base of the second scribe 74′. As theprocess head moves across the substrate in the X direction, the order ofthe five processes carried out to form and complete the interconnectstructure is as follows:—

-   -   1) Carry out 3 laser scribes with first, second and third laser        beams 73, 73′, 73″    -   2) Fill first laser scribe line 74 with insulating ink 76        delivered by first ink jet nozzle 75    -   3) Form conducting bridge across first laser scribe line 74 to        second laser scribe line 74′ with conducting ink 78 delivered by        second ink jet nozzle 77.

Instead of moving the process head over the stationary substrate surfacein the direction X as shown the same sequence of laser and ink jetprocesses is achieved by holding the process head stationary and movingthe panel in the opposite X direction.

FIG. 8 shows the time sequence of the laser and ink jet processesdelivered to the substrate surface by the apparatus shown in FIG. 7.FIG. 8A shows a substrate 81 on which a stack of layers 82 consisting ofa lower electrode layer, an active layer and an upper electrode layerhas been deposited. These layers are applied sequentially without anyintermediate laser processes. FIG. 8B shows the three laser processesthat are then carried out. A first laser scribe 83 is made thatpenetrates all 3 layers as far as the substrate. A second laser scribe84 penetrates the top two layers but not the lower electrode layer. Athird laser scribe 85 penetrates the top electrode layer and may alsopenetrate into the active layer. These three laser scribes can beperformed at exactly the same time or they can be carried outsequentially. The order in which they are made is not critical. Afterall three laser processes have been completed materials are applied byink jet printing. FIG. 8C shows how an insulating fluid 86 is appliedinto the first laser scribe 83 by means of an ink jet nozzle (notshown). The fluid 86 is immediately UV cured or later thermally cured toform a solid. FIG. 8D shows the next step where a fluid 87 that isconducting or contains conducting particles is applied by means of anink jet nozzle (not shown) over the insulating material 86 in the firstscribe 83 and also into the second laser scribe 84. The fluid 87 issubsequently thermally cured to form a solid. The fluid 87 does notextend into the third scribe 85. The conducting material 87 forms abridge over the insulating material 86 to electrically connect the topelectrode layer on the left side to the bottom electrode layer on theright side to connect adjacent cells in series.

FIG. 9 shows a third version of part of apparatus according to a thirdembodiment of the invention. It shows a third arrangement of the threelaser beams and two ink jet nozzles that are attached to the processhead in order to make a single cell interconnect structure. A solarpanel 91 has multiple cells along its length in direction Y. This meansthat interconnections are made by moving the panel 91 with respect tothe process head in the X direction. An area 92 of the panel thatincludes a region where adjacent cells are connected is shown expandedon the right side of the figure and shows part of the moving processhead with its associated laser beams and ink jet nozzles that correspondto a single cell interconnect structure. First, second and third laserbeams 93, 93′ and 93″ respectively make a first scribe 94 through allthree layers, a second scribe 94′ through the top two layers and a thirdscribe 94″ through the top layer. An ink jet nozzle 95 is attached tothe process head and is situated on a line that is parallel to the Xdirection and passes through the position of the first laser beam. Thisnozzle injects a stream of insulating fluid 96 to fill the first laserscribe 94. A second larger ink jet nozzle 97, or multiple smallernozzles, is also attached to the process head and is situated in the Xdirection such that when the process head is moving over the substratethe second ink jet head 97 follows the first ink jet head 95. Thissecond ink jet nozzle 97 injects a stream of conducting fluid 78. Thenozzle 97 is situated in the Y direction such that the fluid 78deposited on the substrate surface forms an electrically conductingbridge over the previously applied insulating fluid 26, the bridgeextending from the upper electrode surface on the left side of the firstscribe 94 to the lower electrode surface at the base of the secondscribe 94′. As the process head moves across the substrate in the Xdirection, the order of the five processes carried out to form andcomplete the interconnect structure is as follows:—

-   -   1) Carry out first laser scribe 94 with first laser beam 93    -   2) Fill first laser scribe line 94 with insulating ink 96        delivered by first ink jet nozzle 95    -   3) Carry out second and third laser scribes 94′ and 94″ with        second and third laser beams 93′ and 93″ respectively    -   4) Form conducting bridge across first laser scribe line 94 to        second laser scribe line 94′ with conducting ink 98 delivered by        second ink jet nozzle 97.

Instead of moving the process head over the stationary substrate surfacein the direction X (as shown), the same sequence of laser and ink jetprocesses can be achieved by holding the process head stationary andmoving the panel in the opposite X direction.

FIG. 10 shows the time sequence of the laser and ink jet processesdelivered to the substrate surface by the apparatus shown in FIG. 9.FIG. 10A shows a substrate 101 on which a stack of layers 102 consistingof a lower electrode layer, an active layer and an upper electrode layerhas been deposited. These layers are applied sequentially without anyintermediate laser processes. FIG. 10B shows the first laser processthat is then carried out. A first laser scribe 103 is made thatpenetrates all three layers as far as the substrate. After the firstlaser beam scribes through the layers, an ink jet process is performed.FIG. 10C shows how an insulating fluid 104 is applied into the firstlaser scribe 103 by means of an ink jet nozzle (not shown). The fluid104 is immediately UV cured or later thermally cured to form a solid.Following this ink jet process second and third laser scribes areperformed. FIG. 10D shows second laser scribe 105 that penetrates thetop two layers but not the lower electrode layer. It also shows thirdlaser scribe 106 that is made parallel to and beside the second scribe105 on the side away from the first scribe 103. This scribe 106 can alsopenetrate partially or fully into the active layer but cannot damage thelower electrode layer. Second and third laser scribes 105, 106 can beperformed at exactly the same time or they can be carried outsequentially. The order in which they are made is not critical. Aftersecond and third laser scribes 105, 106 have been made, the cellinterconnection is completed by the final ink jet printing process. FIG.10E shows the final step where a fluid 107 that is conducting orcontains conducting particles is applied by means of an ink jet nozzle(not shown) over the insulating material in the first scribe 103 andalso into the second laser scribe 105. The fluid 107 is subsequentlythermally cured to form a solid. The fluid 107 does not extend into thethird scribe 106. The conducting material 107 forms a bridge over theinsulating material 104 to electrically connect the top electrode layeron the left side to the bottom electrode layer on the right side toconnect adjacent cells in series.

FIG. 11 shows a fourth version of part of apparatus according to afourth embodiment of the invention. It shows a fourth arrangement of thethree laser beams and two ink jet nozzles that are attached to theprocess head in order to make a single cell interconnect structure. Asolar panel 111 has multiple cells along its length in direction Y. Thismeans that interconnections are made by moving the panel with respect tothe process head in the X direction. An area 112 of the panel thatincludes a region where adjacent cells are connected is shown enlargedon the right side of the figure and shows part of the moving processhead with its associated laser beams and ink jet nozzles that correspondto a single cell interconnect structure. First, second and third laserbeams 113, 113′ and 113″, respectively, make a first scribe 114 throughall three layers, a second scribe 114′ through the top two layers and athird scribe 114″ through the top layer. The figure shows the processhead and attached laser beams moving in the X direction such that on thesubstrate surface the first laser beam 113 is in advance of the second113′ which is likewise in advance of the third 113″. An ink jet nozzle115 is attached to the process head and is situated on a line that isparallel to the X direction and passes through the position of the firstlaser beam 113. This nozzle 115 injects a stream of insulating fluid 116to fill the first laser scribe 114. A second larger ink jet nozzle 117,or multiple smaller nozzles, is also attached to the process head and issituated in the X direction such that when the process head is movingover the substrate the second ink jet head 117 follows the first ink jethead 115. This second ink jet nozzle 117 injects a stream of conductingfluid 118. The nozzle 117 is situated in the Y direction such that thefluid 118 deposited on the substrate surface forms an electricallyconducting bridge over the previously applied insulating fluid 116, thebridge extending from the upper electrode surface on the left side ofthe first scribe 114 to the lower electrode surface at the base of thesecond scribe 114′. As the process head moves across the substrate inthe X direction, the order of the five processes carried out to form andcomplete the interconnect structure is as follows:—

-   -   1) Carry out first and second laser scribes 114, 114′ with first        and second laser beams 113, 113′    -   2) Fill first laser scribe line 114 with insulating ink 116        delivered by first ink jet nozzle 115    -   3) Form conducting bridge across first laser scribe line 114 to        second laser scribe line 114′ with conducting ink 118 delivered        by second ink jet nozzle 117.    -   4) Carry out third laser scribe 114″ with third laser beam 113″

Instead of moving the process head over the stationary substrate surfacein the direction X (as shown), the same sequence of laser and ink jetprocesses can be achieved by holding the process head stationary andmoving the panel in the opposite X direction.

FIG. 12 shows the time sequence of the laser and ink jet processesdelivered to the substrate surface by the apparatus shown in FIG. 11.FIG. 12A shows a substrate 121 on which a stack of layers 122 consistingof a lower electrode layer, an active layer and an upper electrode layerhas been deposited. These layers are applied sequentially without anyintermediate laser processes. FIG. 12B shows the two laser processesthat are then carried out. A first laser scribe 123 is made thatpenetrates all 3 layers as far as the substrate. A second laser scribe124 penetrates the top two layers but not the lower electrode layer.These two laser scribes can be performed at exactly the same time orthey can be carried out sequentially. The order in which they are madeis not critical. After both laser processes have been completedmaterials are applied by ink jet printing. FIG. 12C shows how aninsulating fluid 125 is applied into the first laser scribe 123 by meansof an ink jet nozzle (not shown). The fluid 125 is immediately UV curedor later thermally cured to form a solid. FIG. 12D shows the next stepwhere a fluid 126 that is conducting or contains conducting particles isapplied by means of an ink jet nozzle (not shown) over the insulatingmaterial 125 in the first scribe 123 and also into the second laserscribe 124. The fluid 126 is subsequently thermally cured to form asolid. The conducting material 126 forms a bridge over the insulatingmaterial 125 to electrically connect the top electrode layer on the leftside to the bottom electrode layer on the right side to connect adjacentcells in series. FIG. 12E shows the last step in the interconnectionprocess where a third laser scribe that penetrates the upper layer 127is made parallel to and beside the second scribe on the side away fromthe first scribe. This scribe can also penetrate partially or fully intothe active layer but cannot damage the lower electrode layer. Theadvantage of carrying out this third laser scribe after the conductingink jet application process is that the laser scribe can be used toremove any conducting ink that may have spread across the surface of theupper electrode into the region of the third scribe.

FIG. 13 shows how an individual interconnect process unit as shown inFIG. 5 is expanded into a device that can process multiple interconnectstructures in parallel. 131 is a solar panel with multiple cells alongits length in direction Y. 132 is an area of the panel 131 that includesthe connections between several cells. This area 132 is enlarged on theright of the figure and shows part of the moving process head with itsassociated laser beams and ink jet nozzles that correspond to (in thiscase) 5 cell interconnect structures 133. 134 is a device that positions5 parallel first laser beams 135 along a line. The device can be rotatedabout an axis perpendicular to the paper to set the beam spacingcorrectly in the Y direction. The row of 5 beams makes 5 parallel firstcuts through the 3 layers. 136 is a device that positions 5 parallelsecond laser beams along a line in order to make 5 parallel second cutsthrough the top 2 layers. The device can also be rotated about an axisperpendicular to the paper to set the beam spacing correctly. 137 is adevice that positions 5 parallel third laser beams along a line in orderto make 5 parallel third cuts through the top layer. The device can berotated about an axis into the paper to set the beam spacing correctly.138 is a device that positions 5 parallel first ink jet nozzles 139along a line in order to apply 5 parallel lines of insulating fluid intothe 5 first laser cuts. The device can be rotated about an axisperpendicular to the paper to set the nozzle spacing correctly. 1310 isa device that positions 5 parallel second ink jet nozzles 1311 along aline in order to apply 5 parallel lines of conducting fluid over theinsulating fluid in the 5 first cuts and into the 5 second laser cuts.The device can be rotated about an axis perpendicular to the paper toset the nozzle spacing correctly. The panel 131 and process head aremoved relative to each other in the X direction so that areas of thesubstrate see in succession:—

-   -   1) the row of first laser beams,    -   2) the row of first ink jet heads,    -   3) the row of second laser beams,    -   4) the row of second ink jet heads and    -   5) the row of third laser beams.

FIG. 14 shows how an individual interconnect process unit as shown inFIG. 7 is expanded into a device that can process multiple interconnectstructures in parallel. 141 is a solar panel with multiple cells alongits length Y. 142 is an area of the panel 141 that includes theconnections between several cells. This area 142 is enlarged on theright of the figure and shows part of the moving process head with itsassociated laser beams and ink jet nozzles that correspond to (in thiscase) 5 cell interconnect structures 143. 144 is a device that positions5 parallel first laser beams 145 along a line. The device can be rotatedabout an axis perpendicular to the paper to set the beam spacing in theY direction correctly. The row of 5 beams makes 5 parallel first cutsthrough the 3 layers. 146 is a device that positions 5 parallel secondlaser beams along a line in order to make 5 parallel second cuts throughthe top 2 layers. The device can be rotated about an axis perpendicularto the paper to set the beam spacing correctly. 147 is a device thatpositions 5 parallel third laser beams along a line in order to make 5parallel third cuts through the top layer. The device can be rotatedabout an axis perpendicular to the paper to set the beam spacingcorrectly. 148 is a device that positions 5 parallel first ink jetnozzles 149 along a line in order to apply 5 parallel lines ofinsulating fluid into the 5 first laser cuts. The device can be rotatedabout an axis perpendicular to the paper to set the nozzle spacingcorrectly. 1410 is a device that positions 5 parallel second ink jetnozzles 1411 along a line in order to apply 5 parallel lines ofconducting fluid over the insulating fluid in the 5 first cuts and intothe 5 second laser cuts. The device can be rotated about an axisperpendicular the paper to set the nozzle spacing correctly. The panel141 and process head are moved relative to each other in the X directionso that areas of the substrate see in succession:—

-   -   1) the row of first laser beams,    -   2) the row of second laser beams,    -   3) the row of third laser beams,    -   4) the row of first ink jet nozzles and    -   5) the row of second ink jet nozzles.

FIG. 15 shows part of apparatus according to a fifth embodiment of theinvention. It shows a fifth arrangement of the three laser beams andassociated ink jet nozzles that are attached to the process head inorder to make a single cell interconnect structure. In this case, twofirst ink jet heads and two second ink jet heads are fitted to allowoperation of the head in either direction. A solar panel 151 hasmultiple cells along its length in direction Y. This means thatinterconnections are made by moving the panel with respect to theprocess head in either of the X directions. An area 152 of the panelthat includes a region where adjacent cells are connected is shownenlarged on the right side of the figure and shows part of the movingprocess head with its associated laser beams and ink jet nozzles thatcorrespond to a single cell interconnect structure. First, second andthird laser beams 153, 153′ and 153″, respectively, make a first scribethrough all three layers, a second scribe through the top two layers anda third scribe through the top layer. Two first ink jet nozzles 154,154′ are attached to the process head and are situated on each side ofthe first laser beam on a line that is parallel to the X direction andpasses through the position of the first laser beam 153. These firstnozzles inject a stream of insulating fluid to fill the first laserscribe. Two second, larger, ink jet nozzles, or multiple smallernozzles, 155, 155′ are also attached to the process head and aresituated on each side of the first laser beam on a line that is parallelto the X direction and passes through a position close to the firstlaser beam 153. These second ink jet nozzles inject a stream ofconducting fluid. The nozzles 155, 155′ are situated in the Y directionsuch that the conducting fluid deposited on the substrate surface formsan electrically conducting bridge over the previously applied insulatingfluid, the bridge extending from the upper electrode surface on the leftside of the first scribe to the lower electrode surface at the base ofthe second scribe. As the process head moves across the substrate ineither of the X directions, one or other of each first ink jet nozzleand one or other of the corresponding second ink jet nozzle areactivated such that the order of the five processes carried out to formand complete the interconnect structure is as follows:—

-   -   1) Carry out first, second and third laser scribes with first,        second and third laser beams.    -   2) Fill first laser scribe line with insulating ink delivered by        either first ink jet nozzle 154 or 154′ depending on the head        travel direction    -   3) Form conducting bridge across first laser scribe line to        second laser scribe line with conducting ink delivered by either        second ink jet nozzle 155 or 155′ depending on the head travel        direction.

Instead of moving the process head over the stationary substrate surfacein the direction X (as shown), the same sequence of laser and ink jetprocesses can be achieved by holding the process head stationary andmoving the panel in the opposite X direction.

FIG. 16 shows how an individual interconnect process unit as shown inFIG. 15 is expanded to provide a device that can simultaneously processmultiple interconnect structures in parallel. 161 is a solar panel withmultiple cells along its length Y. 162 is an area of the panel 161 thatincludes the connections between several cells. This area 162 isenlarged on the right of the figure and shows part of the moving processhead with its associated laser beams and ink jet nozzles that correspondto (in this case) 5 cell interconnect structures 163. 164 is a devicethat positions 5 parallel first, second and third laser beams 165 alonga line. Individual beams are not shown. The device can be rotated aboutan axis perpendicular to the paper to set the beam spacing in the Ydirection correctly. The row of 5 sets of first, second and third beamsmakes 5 parallel first cuts through the 3 layers, 5 parallel second cutsthrough the second and third layers and 5 parallel third cuts throughthe top layer. 166 and 166′ are devices that each position 5 parallelfirst ink jet nozzles along a line in order to apply 5 parallel lines ofinsulating fluid into the 5 first laser cuts. The devices can be rotatedabout axes perpendicular to the paper to set the nozzle spacingcorrectly. Either set of first ink jet nozzles 166 or 166′ is activateddepending on the direction of travel of the process head in the Xdirection with respect to the substrate surface such that the insulatingink application follows the first laser cut. 167 and 167′ are devicesthat each position 5 parallel second ink jet nozzles along a line inorder to apply 5 parallel lines of conducting fluid over the insulatingfluid in the 5 first cuts and into the 5 second laser cuts. The devicescan be rotated about axes perpendicular the paper to set the nozzlespacing correctly. Either set of second ink jet nozzles 167 or 167′ isactivated depending on the direction of travel of the process head inthe X direction with respect to the substrate surface such that theconducting ink application follows the insulating ink application whichfollows the first and second laser cuts. The panel 151 and process headare moved relative to each other in either X direction so that areas ofthe substrate see in succession:—

-   -   1) the row of first, second and third laser beams,    -   2) a row of first ink jet nozzles and    -   3) a row of second ink jet nozzles.

FIG. 17 shows apparatus by means of which the beam from a single laserunit is divided to form one set of first, second and third laser beamsin order to create a single cell to cell interconnect structure on thesubstrate. First and second ink jet heads that are associated with thethree laser beams are not shown in the figure. Pulsed laser unit 171emits a beam 172 that is directed by mirror 173 through focussing lens174 to form a focal spot on the surface of the substrate 175.Diffractive optical element (DOE) 176 situated in the beam splits thebeam into three angularly separated beams each of which is focussed bylens 174 to create a line of three focal spots 177 on the substratesurface corresponding to the first, second and third laser beamsassociated with a single interconnect structure. The properties of thelaser beam 172 and the focal length of the lens 174 define the size ofthe focal spots on the surface. The design of the DOE 176 defines theangular spacing between the three beams and hence, together with thelens focal length, the separation of the spots on the substrate surface.The DOE can also be designed to control the relative laser power in eachspot to match the separate requirements for the first, second and thirdlaser cut processes. Rotation of the DOE allows adjustment of the focalspot spacing in the direction perpendicular to the direction of travel.The use of DOEs for splitting laser beams into multiple separate beamsis well known.

In practice, laser spot sizes in the range 0.05 mm to 0.1 mm are usedwith inter-spot spacings of two or three times the spot diameter. Thelaser power required in the first beam in order to perform the first cutthrough all three layers to the substrate surface is generallysignificantly higher than that required in the second and third beams.For example, for a solar panel consisting of a lower electrode layer ofMolybdenum, an active layer of CIGS and an upper electrode layer of ZnOwith an IR laser generating laser spots with diameters of 0.1 mm movingat a speed of 200 mm per second over the substrate surface, a laserpower in the first beam in the range 5 W to 10 W has been found to makea satisfactory first cut whereas powers of only a few W are required inthe second and third beams for the second and third cuts.

FIGS. 18A and 18B show another example of apparatus by means of whichthe beam from a single laser unit is divided to form one set of first,second and third laser beams in order to create a single cell to cellinterconnect structure on the substrate. FIG. 18A shows a plan view of around laser beam 181 falling on a special truncated transmissivebi-prism 182. Region 183 in the centre of the device is a flat regionseparating two prismatic regions 184, 184′. The centre of the bi-prismis displaced from the centre of the beam. FIG. 18B shows a side view ofthe laser beam 181 passing through special truncated bi-prism 182 anddividing it into three separate angularly separated beams 185, 186 187.The part of the laser beam 181 that is incident on the flat part of thedevice 183 passes through the device without deviation to form beam 185.The parts of the laser beam that pass through the two prismatic parts ofthe device 184, 184′ are deviated to form beams 186 and 187,respectively. Due to the displacement of the bi-prism from the centre ofthe laser beam more laser power is delivered in beam 187 compared tobeam 186. By adjustment of the width of the truncated region of thebi-prism 183 and displacement of the bi-prism centre from the beamcentre the power in each beam can be set to a required level. The use ofbi-prisms of various types for dividing beams into two or more angularlyseparated beams is well known.

FIG. 19 shows apparatus by means of which the prismatic device shown inFIG. 18 is used to divide the beam from a single laser unit to form oneset of first, second and third laser beams in order to create a singlecell to cell interconnect structure on the substrate. First and secondink jet heads that are associated with the three laser beams are notshown in the figure. Pulsed laser unit 191 emits a beam 192 that isdirected by mirror 193 through focussing lens 194 to form a focal spoton the surface of the substrate 195. Truncated bi-prism device 196situated in the beam splits the beam into three angularly separatedbeams each of which is focussed by lens 194 to create a line of threefocal spots 197 on the substrate surface corresponding to the first,second and third laser beams associated with a single interconnectstructure. The properties of the laser beam 192 and the focal length ofthe lens 194 define the size of the focal spots on the surface. Thedesign of the truncated bi-prism device 196 defines the angular spacingbetween the three beams and hence, together with the lens focal length,the separation of the spots on the substrate surface. The bi-prism canalso be designed to control the relative laser power in each spot tomatch the separate requirements for the first, second and third lasercut processes. Rotation of the bi-prism about an axis through its centreand normal to its surface allows adjustment of the focal spot spacing inthe direction perpendicular to the direction of substrate travel.

FIG. 20 shows apparatus by means of which the beam from a first laserunit is divided to form two of the first, second or third laser beamswhich are then combined with the beam from a second laser to form threebeams in total in order to create a single cell to cell interconnectstructure on the substrate. First and second ink jet heads that areassociated with the three laser beams are not shown in the figure.Pulsed first laser unit 201 emits a beam 202 that is directed by beamcombining mirror 203 through focussing lens 204 to form a focal spot onthe surface of the substrate 205. Optical element 206 which can be a DOEor a bi-prism situated in the beam 202 splits the beam into twoangularly separated beams each of which is focussed by lens 204 tocreate two focal spots 207, 207′ on the substrate surface correspondingto any two of the first, second or third laser beams associated with asingle interconnect structure. The properties of the laser beam 202 andthe focal length of the lens 204 define the size of the focal spots onthe surface. The design of the DOE or bi-prism 206 defines the angularspacing between the two beams and hence, together with the lens focallength, the separation of the spots on the substrate surface. Rotationof the DOE or bi-prism about an axis through its centre andperpendicular to its surface allows adjustment of the focal spot spacingin the direction perpendicular to the direction of substrate travel.

Second laser unit 208 emits beam 209 that is directed by mirror 2010through beam combining mirror 203 and through focussing lens 204 to forma focal spot 2011 on the surface of the substrate 205. Adjustment ofmirror 2010 allows the focal spot produced by the second laser 2011 tobe located at any desired position on the substrate surface with respectto the two spots created by the first laser beam 207, 207′. The secondlaser unit 208 can have the same or different wavelength of operation tothe first laser unit 201. If the wavelengths of the first and secondlasers are the same the beam combining mirror 203 is polarization,sensitive so that it transmits a beam that is incident with so calledp-polarization and reflects a laser beam that has so calleds-polarisation. In the case shown in the figure, first laser 201 wouldthus be s-polarized and second laser 208 would be p-polarised at thebeam combining mirror 203. Using two lasers of the same wavelengthallows operation of one laser scribe at a different repetition rate andpulse length to the other two laser scribes. If the wavelengths of thefirst and second lasers are different then the beam combining mirror 203is wavelength sensitive so that it reflects the beam from the firstlaser 201 and transmits the beam from the second laser 208. Beamdivergence compensation optics 2012 situated in one or both beams aregenerally required when using a common focussing lens for focussing thebeams from two lasers onto the substrate. This is especially importantwhen the beams have different wavelengths but is also desirable when thewavelengths are the same. Using two lasers of different wavelengthallows operation of one laser scribe at a different wavelength to theother two laser scribes. Such an arrangement is often advantageous interms of making cuts in the upper two layers without damaging the firstlayer. Preferred laser wavelengths for making the various laser cuts arein the IR, visible and UV ranges. Particular examples are 1064 nm, 532nm or 355 nm. Use of beam combining mirrors of polarisation type orwavelength sensitive (so called di-chroic) type is well known.

FIG. 21 shows apparatus appropriate for carrying out the cellinterconnection process on a thin film solar panel. Solar panel 211 ismounted on flat chuck plate 212 which is mounted on translation stages213 and 213′ driven by servo motors 214, 214′ so that the panel is ableto move in two orthogonal directions X and Y parallel to the edges ofthe panel. The beam from laser unit 215 is directed by mirrors 216, 216′to a process head 217 that is mounted over the panel. Details of theoptics in the process head to split the beam into first, second andthird laser beams as well as the associated first and second ink jetheads on the process head are not shown in the figure. In operation, theprocess head is stationary and the panel is moved in a series of linearmoves in the Y direction each pass across the substrate being followedby a step in the X direction. The process head may process a single cellinterconnect on each pass or in a preferred situation may processmultiple interconnects on each pass. The figure shows a stationaryprocess head with the substrate moving in two axes but in practice otherarrangements are possible. A preferred arrangement has the substratemoving in one axis and the process head moving in the other. Anarrangement where the process head moves in two orthogonal axes over astationary substrate is also possible.

FIG. 22 shows apparatus appropriate for controlling the equipment shownin FIG. 21. Control unit 221 generates signals that control the laser222, the stage servo motors 223, 223′ and the ink jet print headcontroller 224, associated ink jet delivery system 225 and ink jet printheads mounted in process head 226. In the embodiments described above,the first second and third cuts are all formed using a laser beam to cutthrough the relevant layer(s). Whilst, in many cases, this is thepreferred method of forming the cuts, one or more of the cutter units onthe processing head may comprise other forms of cutter means. Anotherway to form a cut though one or more layers is by the use of amechanical scriber, such as a fine wire or multiple parallel styli,carried by a precision unit such as manufactured by LehmannPräzisionstechnik GmbH. Thus, one or more of the lasers in theembodiments described above may be replaced by a mechanical scriber.

In many cases, the first cut will be formed using a laser but the secondand third cuts can be formed by laser or by a mechanical scriber.However, all cuts could be formed by laser (as described above) or allcuts could be formed by mechanical scriber or any combination of laserand mechanical scriber.

The invention claimed is:
 1. A method for dividing a thin film devicehaving a first layer which is a lower electrode layer, a second layerwhich is an active layer and a third layer which is an upper electrodelayer, all the layers being continuous over the device, into separatecells which are electrically interconnected in series, the dividing ofthe cells and the electrical connection between adjacent cells all beingcarried out in a single pass of a process head across the device, theprocess head performing the following steps in the single pass: a)making a first cut through the first, second and third layers; b) makinga second cut through the second and third layers, the second cut beingadjacent to the first cut; c) making a third cut through the third layerthe third cut being adjacent to the second cut and on the opposite sideof the second cut to the first cut; d) using a first ink jet print headto deposit a non-conducting material into the first cut; and e) using asecond ink jet print head to apply conducting material to bridge thenon-conducting material in the first cut and either fully or partiallyfill the second cut such that an electrical connection is made betweenthe first layer and the third layer, wherein step (a) precedes step (d),step (d) precedes step (e) and step (b) precedes step (e), otherwise thesteps may be carried out in any order in the single pass of the processhead across the device.
 2. A method as claimed in claim 1 in which theorder in which the steps are carried out in the single pass isdetermined by the relative positions on the process head of the firstand second ink jet print heads and components on said process head forforming said first, second and third cuts.
 3. A method as claimed inclaim 1 in which one or more of the first, second and third cuts areformed using one or more laser beams.
 4. A method as claimed in claim 1in which one or more of the first, second and third cuts are formedusing one or more mechanical scribers.
 5. A method as claimed in claim 1in which the process head is able to carry out all said steps in asingle pass in either or both directions across the thin film device. 6.A method as claimed in claim 1 in which one or more curing steps arecarried out to cure said non-conducting material and/or said conductingmaterial after deposition into the respective cut.
 7. A method asclaimed in claim 6 in which one or more of said curing steps are carriedout during said single pass after deposition of the non-conductingmaterial and/or said conducting material.
 8. A method as claimed inclaim 6 in which one or more of said curing steps are carried out inseparate apparatus after said single pass.
 9. A method as claimed in aclaim 1 in which the thin film device is one of the following: a solarpanel, a lighting panel and a battery.
 10. An apparatus for dividing athin film device having a first layer which is a lower electrode layer,a second layer which is an active layer and a third layer which is anupper electrode layer, all the layers being continuous over the device,into separate cells which are electrically interconnected in series, theapparatus comprising a process head on which are provided: a) one ormore cutters positioned on the process head to make, during a singlepass cutter units for malting a first cut through the first, second andthird layers, a second cut through the second and third layers adjacentto the first cut and a third cut through the third layer adjacent to thesecond cut and on the opposite side of the second cut to the first cut;b) a first ink jet print head positioned on the process head to depositfor depositing a non-conducting material into the first cut during thesingle pass; and c) a second ink jet print head positioned on theprocess head to apply for applying conducting material to bridge thenon-conducting material in the first cut and either fully or partiallyfill the second cut during the single pass so that an electricalconnection is made between the first layer and the third layer, theapparatus also comprising: d) a drive that moves the process headrelative to the device; and e) a controller adapted to control means forcontrolling movement of the process head relative to the device and toactuate the one or more cutters and the first and second ink jet printheads so that division of the device into separate cells and theformation of an electrical connection between adjacent cells can all becarried out in the single pass of the process head across the device.11. Apparatus as claimed in claim 10 in which the one or more cutterscomprises a single pulsed laser to form the first, second and thirdcuts.
 12. Apparatus as claimed in claim 10 in which the one or morecutters comprise pulsed lasers of two or more types to form the first,second and/or third cuts.
 13. Apparatus as claimed in claim 11 whichcomprises a focussing lens to deliver first, second and third laserbeams to the device, an angular deviation is provided between the beamssuch that the focal spots at a focus of the lens formed by the first,second and third laser beams have a required spatial separation on asurface of the device surface to form the first, second and third cuts.14. Apparatus as claimed in claim 11 comprising a diffractive opticalelement to split a laser beam from a pulsed laser to form first, secondand third laser beams to form the first, second and third cuts. 15.Apparatus as claimed in claim 11 comprising a prismatic optical elementto split a laser beam from a pulsed laser to form first, second andthird laser beams to form the first, second and third cuts. 16.Apparatus as claimed in claim 11 comprising a diffractive opticalelement to split a laser beam from a first pulsed laser to form any twoof the first, second and third laser beams, and a second pulsed laser toprovide the remaining laser beam arranged such that beams from the firstand second pulsed lasers combine to form three spatially separated laserspots on the surface of the device for to form the first, second andthird cuts.
 17. Apparatus as claimed in claim 11 comprising a prismaticoptical element of bi-prism type to split a laser beam from a firstpulsed laser to form any two of the first, second and third laser beams,and a second pulsed laser to provide the remaining laser beam arrangedsuch that the beams from the first and second pulsed lasers combine toform three spatially separated laser spots on the surface of the deviceto form the first, second and third cuts.
 18. Apparatus as claimed inclaim 10 in which the drive comprises a dual axis servo motor to movethe process head relative to the device in two orthogonal directions.19. Apparatus as claimed in claim 10 in which the controller is arrangedso that the device and process head move relative to each other in afirst direction parallel to the lengths of the first and second cuts ina continuous path across the device and at the end of the path to stepin a direction perpendicular to the first direction by a predetermineddistance equal to the width of the cells to be formed in the device.